Ensure base image of the same tag is used for demo image

Author: manisandro

.github/workflows/main.yml

@@ -36,7 +36,7 @@ jobs:
           fi
           echo "app_version=${GITHUB_REF:10}" >>$GITHUB_OUTPUT
 
-      - name: Build and publish base container
+      - name: Build and publish base image
         uses: elgohr/Publish-Docker-Github-Action@v5
         if: github.event_name != 'pull_request'
         with:
@@ -45,15 +45,16 @@ jobs:
           password: ${{ secrets.DOCKER_HUB_PASSWORD }}
           tags: "${{ steps.get_tag.outputs.tag }}"
 
-      - name: Build and publish demo container
+      - name: Build and publish demo image
         uses: elgohr/Publish-Docker-Github-Action@v5
         if: github.event_name != 'pull_request'
         env:
           QWC2_URL: https://github.com/qgis/qwc2-demo-app/releases/download/${{ steps.get_tag.outputs.app_version }}/qwc2-demo-app.zip
+          BASE_IMAGE_VERSION: ${{ steps.get_tag.outputs.app_version }}
         with:
           name: sourcepole/qwc-map-viewer-demo
           username: ${{ secrets.DOCKER_HUB_USER }}
           password: ${{ secrets.DOCKER_HUB_PASSWORD }}
           tags: "${{ steps.get_tag.outputs.tag }}"
           dockerfile: Dockerfile-qwc2-app
-          buildargs: "QWC2_URL"
+          buildargs: QWC2_URL,BASE_IMAGE_VERSION

Dockerfile-qwc2-app

@@ -1,4 +1,5 @@
-FROM sourcepole/qwc-map-viewer-base:latest
+ARG BASE_IMAGE_VERSION=latest-lts
+FROM sourcepole/qwc-map-viewer-base:$BASE_IMAGE_VERSION
 
 ARG QWC2_URL
 # Optional token for download with authorization